OCCURRENCE OF FREE CREATINE, PHOSPHOCREATINE AND CREATINE-PHOSPHOKINASE IN ADIPOSE-TISSUE

Brown and white adipose tissues were evaluated for the presence of creatine, phosphocreatine and creatine phosphokinase activity. In rats 3.6 and 0.4 .mu.mol of total creatine were found per g wet wt of brown and white adipose tissues, respectively. Creatine was identified by TLC after a pulse label of [14C]creatine was given in vivo. Free creatine and phosphocreatine were determined by column chromatography. Of the total creatine of brown adipose tissue, approximately 1/3-1/2 were attributable to phosphocreatine. The activity of creatine phosphokinase was demonstrated in both white and brown adipose tissue, the values of the latter prevailing over those of the former by a factor of 200, if based on wet wt, or 50, if expressed as specific enzyme activity. The labeling of total creatine in vivo proceeded much faster in adipose tissue than in skeletal muscle. The energy metabolism of adipose is probably closely dependent on the presence of creatine. The specific activities of free creatine and phosphocreatine of brown adipose tissue differed strikingly as long as 24 h after radioactive creatine was injected; this difference points to a metabolic or structural compartmentation of creatine.